In general, there may exist complicatedly a macrocell, a microcell and a picocell in the same service band, in constructing hierarchical cells in a radio communication system.
Describing a case of the macrocell as an upper cell and the microcell as a lower cell, the same service band indicates any one service band out of communicating methods having mutually different service bands such as a cellular movable communication based on a code division multiplexing access (CDMA), a personal communication system (PCS) etc.
At these days, a global system for mobile communication (GSM) employs a hierarchical cell structure between a pacific digital cellular (PDC) and a personal handyphone system (PHS). However, the GSM hierarchical cell structure is provided to form hierarchical cells between mutually different service bands to which mutually different frequency bands are allocated.
Meantime, there is also much even in the CDMA system a concept of forming the hierarchical cell between the mutually different service bands. That is, at present, it is classified into the cellular mobile communication service band, a PCS service band and a next generation mobile communication (IMT-2000) service band, to apply them to the hierarchical cell structure through a lot of research.
However, it is getting required a handoff system between the hierarchical cells, which is applicable to the respective service bands such as the same cellular mobile communication service band, the PCS service band and the next generation mobile communication (IMT-2000) service band etc. Further, it be getting required a function in which a service for the macrocell and the microcell is valid with a single mode mobile station not a double mobile station structure and a handoff between the macrocell and the microcell can be supported.